Assistance system for measuring workload in the rehabilitation process after surgery on the lower extremities

Abstract

The invention relates to a sole construction for use in rehabilitation, consisting of individual truncated cones for transferring the total force acting on the sole to individual pressure sensors with an associated electronic evaluation unit, wherein the pressure points are positioned according to the natural pressure distribution of the foot. By integrating the truncated cone construction and the electronic evaluation unit into an orthopedic insole, cost-effective load measurement during the rehabilitation process can be achieved by evaluating the pressure exerted by the sensors attached to the main pressure points of the sole.

Description

2.1 Technical area

[0001] The invention is located in the medical field of foot pressure measurement. An orthopedic insole measures the pressure exerted on the sole inside the shoe. Electrical pressure sensors are read by an electronic circuit, and the data is processed. 2.2 State of the art

[0002] Currently, products for measuring pressure load on the foot primarily use many individual sensors, thus measuring the pressure load selectively on individual areas of the sole (see patent DE 20 2022 107 097 U1). This can then be used to approximate the total load using mathematical models. This approach corresponds to the implementation of a pressure distribution measurement and requires a high level of circuitry and information technology expenditure. There are also individual patents that describe the integration of a simplified sensor system into a sole (see patent CN 1 11 011 990 A). This also describes the concept of insole foot pressure measurement during a patient's rehabilitation process. Patent DE 20 2019 004 802 U1 also describes the adaptation of the sole design to different patient and shoe types.Patent DE 10 2017 100 636 A1 also refers in its description to the application in "rehabilitation or convalescence after surgery" in the form of a shoe insole, in which force sensors are intended to generate a measurement signal that indicates the load on the foot. Patent CN 1 11 011 990 A also refers to the arrangement of integrated "pressure-absorbing projections or protuberances" that are intended to divert the total load to individual pressure sensors. These are integrated into the sole in the areas where the natural pressure distribution of the foot occurs. The patient's sole can rest directly on the main body of the sole. The use of thin-film resistance pressure sensors arranged in an annular groove is also explicitly described here.Patents DE 10 2017 100 636 A1 and DE 20 2019 004 802 U1 also explain the principle of integrating and connecting an electronic evaluation unit to at least one force sensor via electrical lines. Several force measurement signals are averaged to generate a feedback control signal. A feedback signal is only output when the evaluation unit detects incorrect or excessive loading of the foot. This occurs when a threshold value of the averaged force signal or of an individual force sensor is exceeded. A feedback control signal is generated that provides tactile feedback in the area of ​​the shoe insole. In addition, both an acoustic signal and optical light signals are provided for load monitoring. 2.3 Problem

[0003] The underlying problem relates to its use in rehabilitation centers. Here, patients are gradually reintroduced to full weight-bearing after surgery on their lower extremities. Current procedures rely solely on a standard body scale. During the rehabilitation process, the patient can stand on it with one foot and gradually increase the load. This allows them to gain a feel for the appropriate load limit. The rehabilitation exercises are then performed. Without a scale, however, it is no longer possible to monitor whether the patient is adhering to the limits. In addition to excessive loading, underloading would also be critical, as both cases would slow down the rehabilitation process.

[0004] Current products utilize a high sensor density to enable pressure distribution across the entire sole of the foot. However, there is not a sensor at every point on the sole, and the total load is only approximated by a complex computer program. The combination of these two results in a high price and features that are unnecessary for use in rehabilitation clinics. Therefore, these products are more commonly used by orthopedic surgeons to measure the foot in order to diagnose conditions and produce suitable shoes or orthopedic insoles. Furthermore, existing solutions focus primarily on measuring pressure distribution on the sole of the foot. However, some solutions that determine the total pressure are very inaccurate, as pressure can also be dissipated at locations other than the sensor. This leads to significant deviations, and the exact load on the sole of the foot is not determined. 2.4 Invention

[0005] The invention is intended to enable a system to support the rehabilitation process with partial weight bearing after surgery on the lower extremities, with reduced sensor requirements through targeted force distribution structures in the sole construction. The aim is to simplify this complex process and calculate the total pressure directly and not just as a mathematical model. For this purpose, a support structure was developed which diverts the pressure on the foot to a few sensors. This allows the sensor density to be reduced while still determining the total load on the sole. The sole is composed of several individual free-form parts. These are roughly shaped like a truncated cone, with the combined base surfaces forming the sole shape. The other side of the stump serves as the pressure surface for the sensor. By adapting the surface, different sensor types can be used.Thin-film resistance sensors, for example, can be used. However, for this design, a load cell sensor of the type FX292X-100A-0200-L was used. This sensor was characterized by its high accuracy and the resulting low measurement deviations. To determine the optimal position of the pressure points, the natural pressure distribution in the sole of the foot was used as a guide. In many tests, the position of the sensors was adjusted so that they were located where the highest loads occur. This ensures a stable stand and high measurement accuracy. In the tests, a number of six sensors was found to be sufficient. This way, the sole remains flexible but does not wobble, and the most important pressure points in the foot can be covered.

[0006] The truncated cones were manufactured using rapid prototyping with a fused deposition modeling (FDM) printer. This process allows the truncated cones to be adapted directly to the patient's foot. For example, a different pressure distribution can be taken into account and the position of the pressure points can be adjusted to suit the patient. Furthermore, the manufacturing process allows for the adjustment of the sole surface, creating orthopedic insoles. This makes the invention ideal for patients undergoing rehabilitation.

[0007] An electronic circuit with a microcontroller is used to evaluate the measured values. The measurement signals are amplified and then digitized. The digitized values ​​from the individual sensors are added together to calculate the total load on the foot. This value can then be compared with a limit value. This is done using various buttons, and depending on the magnitude of the measured value compared to the limit value, a visual and acoustic signal is emitted. For example, a beep sounds if the limit value is exceeded. Alternatively, the device can also be connected wirelessly to a mobile device, such as a smartphone or smartwatch. The limit value can then be set and the actual value read. This also opens up new signaling possibilities.A vibration on the wrist proved to be a particularly suitable option, as it distracts the patient less than an optical or acoustic signal. 2.5 Options for commercial registration

[0008] The invention can be marketed directly in this form. A potential product can be manufactured in two different ways. The first variant involves uniform production for the mass market. Soles are produced in different shoe sizes but otherwise identical in shape. These can then be sold to rehabilitation clinics and used during treatment. Since the soles are reusable, they are simply disinfected after each use and then reapplied.

[0009] A second marketing option is the production of customized medical devices. In this case, patients can have a pressure distribution measurement performed by an orthopedic surgeon before surgery. Based on this data, the CAD model can be adjusted, and the sole can then be printed. It is also possible to make adjustments that support an upright and healthy gait. The result is a completely customized product that is sold to the patient and supports their recovery. The sole can also be used at home, further accelerating the rehabilitation process. Ideally, health insurance companies would support the use of the soles and cover the costs. 2.6 Beneficial effect on the state of the art

[0010] The advantageous effect of the invention on the current state of the art can be seen in several areas. The invention directly solves the problem of weight measurement in the shoe sole and eliminates the need for complex computational models. This also allows the number of sensors to be minimized. Where previously a large number of sensors were used, six sensors per sole are now sufficient. This reduces costs and makes the invention accessible to a wider spectrum of patients. This allows the goal of making user-friendly rehabilitation and healthcare available to a larger number of people to be achieved. Particularly in view of the shortage of skilled personnel in the healthcare sector, it could therefore be advantageous to support staff in rehabilitation clinics with this invention in order to save time that is more urgently needed elsewhere.In addition, fewer sensors also reduce the amount of resources required. The support structures can be made from recycled plastic, reducing the use of critical raw materials such as metals, which would be necessary for a high sensor density. 2.7 Possibility of implementing the invention

[0011] The invention can be implemented in the form of an insole. For this purpose, a substructure is first created using additive manufacturing, as shown in Figure This consists of six truncated cone geometries, whose tips point toward the main stress regions of the sole of the foot. The construction is made of PLA (polylactide). The sensor case is attached beneath the stumps (see drawing). ). This is also manufactured from PLA using additive manufacturing. The pressure sensors in the form of the FX292X-100A-0200-L load cell are located in the sensor cases below the truncated cones.

[0012] The truncated cones represent the entire shape of the sole of the foot and can be placed together and glued to a flexible upper sole. This creates a fully functional insole that's ready for use. To improve comfort, orthopedic padding or a custom-fit overlay can be glued on.

[0013] The FX292X-100A-0200-L sensors are connected to a central evaluation unit on the patient's ankle using jumper wires. When loaded, the load cells output a change in the voltage across them. This voltage change is very small and is therefore amplified using an INA 125P instrumentation amplifier. The amplified voltage signal can be fed to the analog input of a microcontroller (Arduino nano ioT). The Arduino's internal A / D converter converts the analog voltage signal into a digital signal. The digital signals from the six load cells can then be converted into a weight value internally in the Arduino using the characteristic curve and added together. The entire data processing can be varied by programming the software. The weight value is displayed on an LCD. Furthermore, a load limit can be set using control buttons.If this value is exceeded, a warning tone sounds using the KY-006 (Passive Piezo Buzzer) and an LED lights up.

[0014] The entire electronics are mounted on a circuit board in a housing on the ankle. The external power supply, powered by 9V batteries, is also located at this position. The circuit board design is shown in Figure shown. 3 patent claims 1. Sole construction for use in rehabilitation consisting of individual truncated cones for dissipating the total force acting on the sole to individual pressure sensors, wherein the pressure points are positioned according to the natural pressure distribution of the foot, wherein the sole construction is composed of several individual parts in free form which have the shape of a truncated cone, and wherein the combined base surfaces of the individual parts result in a sole shape, and wherein the other side of the truncated cone serves as a pressure surface for the pressure sensor. 2. Sole construction according to claim 1, in which the ends of the truncated cones terminate in sensor-specific pressure stamps which precisely replicate the shape of different sensor types and thus enable the use of different sensor systems. 3. Sole construction according to claim 1, in which pressure sensors are mounted force-fittingly on the truncated cones and the sensor data are evaluated via an electronic circuit. 4. Sole construction with sensors according to claim 3, in which the setting of a load limit value is possible via input elements, the total pressure is digitally determined by summing the sensor measured values ​​and an optical, acoustic or haptic signal is emitted when the limit value is exceeded. 5. Sole construction according to claim 1, in which the shape and size of the truncated cone construction are adapted to the individual requirements of the patient's sole, whereby orthopedic insoles can also be manufactured according to the truncated cone principle for measuring the total pressure load. 6. Sole construction according to claim 1, wherein the sole material is made of recycled PLA, resources can be saved by using a smaller number of sensors and a sustainable product is created.

Claims

[1] Sole construction for use in rehabilitation from individual truncated cones to derive the total force acting on the sole to individual pressure sensors, whereby the pressure points are placed according to the natural pressure distribution of the foot, whereby the sole construction is composed of several individual parts in free form, which have the shape of a truncated cone, and whereby the combined base surfaces of the individual parts result in a sole shape, and whereby the other side of the truncated cone serves as a pressure surface for the pressure sensor. [2] Sole construction according to claim 1, in which the ends of the truncated cones end in sensor-specific pressure stamps which precisely reproduce the shape of different sensor types and thus enable the use of different sensor systems. [3] Sole construction according to claim 1, in which pressure sensors are mounted force-fittingly on the truncated cones and the sensor data are evaluated via an electronic circuit. [4] Sole construction with sensors according to claim 3, in which the setting of a load limit value is possible via input elements, the total pressure is digitally determined by summing the sensor measured values ​​and an optical, acoustic or haptic signal is given when the limit value is exceeded. [5] Sole construction according to claim 1, in which the shape and size of the truncated cone construction are adapted to the individual requirements of the patient's sole, whereby orthopaedic insoles can also be manufactured according to the truncated cone principle for measuring the total pressure load. [6] Sole construction according to claim 1, wherein the sole material is made of recycled PLA, resources can be saved by using a smaller number of sensors and a sustainable product is created.

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